7 files changed, 324 insertions, 233 deletions
diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 556c664019..27e03fe23b 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -312,10 +312,14 @@ module Prism
     # A Location object representing the location of this error in the source.
     attr_reader :location
 
+    # The level of this error
+    attr_reader :level
+
     # Create a new error object with the given message and location.
-    def initialize(message, location)
+    def initialize(message, location, level)
       @message = message
       @location = location
+      @level = level
     end
 
     # Implement the hash pattern matching interface for ParseError.
@@ -325,7 +329,7 @@ module Prism
 
     # Returns a string representation of this error.
     def inspect
-      "#<Prism::ParseError @message=#{@message.inspect} @location=#{@location.inspect}>"
+      "#<Prism::ParseError @message=#{@message.inspect} @location=#{@location.inspect} @level=#{@level}>"
     end
   end
 
@@ -337,20 +341,24 @@ module Prism
     # A Location object representing the location of this warning in the source.
     attr_reader :location
 
+    # The level of this warning
+    attr_reader :level
+
     # Create a new warning object with the given message and location.
-    def initialize(message, location)
+    def initialize(message, location, level)
       @message = message
       @location = location
+      @level = level
     end
 
     # Implement the hash pattern matching interface for ParseWarning.
     def deconstruct_keys(keys)
-      { message: message, location: location }
+      { message: message, location: location, verbose_only: verbose_only }
     end
 
     # Returns a string representation of this warning.
     def inspect
-      "#<Prism::ParseWarning @message=#{@message.inspect} @location=#{@location.inspect}>"
+      "#<Prism::ParseWarning @message=#{@message.inspect} @location=#{@location.inspect} @level=#{@level}>"
     end
   end
 
diff --git a/prism/diagnostic.c b/prism/diagnostic.c
index ed47a1cdad..112ee4ddee 100644
--- a/prism/diagnostic.c
+++ b/prism/diagnostic.c
@@ -1,5 +1,14 @@
 #include "prism/diagnostic.h"
 
+/** This struct holds the data for each diagnostic. */
+struct diagnostic_data {
+    /** The message associated with the diagnostic. */
+    const char* message;
+
+    /** The level associated with the diagnostic. */
+    pm_diagnostic_level_t level;
+};
+
 /**
  * ## Message composition
  *
@@ -49,238 +58,254 @@
  *   - e.g., "INVALID_NUMBER_DECIMAL" is better than "DECIMAL_INVALID_NUMBER".
  *   - When in doubt, look for similar patterns and name them so that they are grouped when lexically
  *     sorted. See PM_ERR_ARGUMENT_NO_FORWARDING_* for an example.
+ *
+ * ## Level
+ *
+ * See pm_diagnostic_level_t for the available levels.
+ * For warning, they are either:
+ * PM_WARNING_VERBOSE_NOT_NIL if they appear for `ruby -c -e 'code'`,
+ * or PM_WARNING_VERBOSE_TRUE if they appear only with -w: `ruby -w -c -e 'code'`.
  */
-static const char* const diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
-    [PM_ERR_ALIAS_ARGUMENT]                     = "invalid argument being passed to `alias`; expected a bare word, symbol, constant, or global variable",
-    [PM_ERR_AMPAMPEQ_MULTI_ASSIGN]              = "unexpected `&&=` in a multiple assignment",
-    [PM_ERR_ARGUMENT_AFTER_BLOCK]               = "unexpected argument after a block argument",
-    [PM_ERR_ARGUMENT_AFTER_FORWARDING_ELLIPSES] = "unexpected argument after `...`",
-    [PM_ERR_ARGUMENT_BARE_HASH]                 = "unexpected bare hash argument",
-    [PM_ERR_ARGUMENT_BLOCK_FORWARDING]          = "both a block argument and a forwarding argument; only one block is allowed",
-    [PM_ERR_ARGUMENT_BLOCK_MULTI]               = "multiple block arguments; only one block is allowed",
-    [PM_ERR_ARGUMENT_FORMAL_CLASS]              = "invalid formal argument; formal argument cannot be a class variable",
-    [PM_ERR_ARGUMENT_FORMAL_CONSTANT]           = "invalid formal argument; formal argument cannot be a constant",
-    [PM_ERR_ARGUMENT_FORMAL_GLOBAL]             = "invalid formal argument; formal argument cannot be a global variable",
-    [PM_ERR_ARGUMENT_FORMAL_IVAR]               = "invalid formal argument; formal argument cannot be an instance variable",
-    [PM_ERR_ARGUMENT_FORWARDING_UNBOUND]        = "unexpected `...` in an non-parenthesized call",
-    [PM_ERR_ARGUMENT_IN]                        = "unexpected `in` keyword in arguments",
-    [PM_ERR_ARGUMENT_NO_FORWARDING_AMP]         = "unexpected `&` when the parent method is not forwarding",
-    [PM_ERR_ARGUMENT_NO_FORWARDING_ELLIPSES]    = "unexpected `...` when the parent method is not forwarding",
-    [PM_ERR_ARGUMENT_NO_FORWARDING_STAR]        = "unexpected `*` when the parent method is not forwarding",
-    [PM_ERR_ARGUMENT_SPLAT_AFTER_ASSOC_SPLAT]   = "unexpected `*` splat argument after a `**` keyword splat argument",
-    [PM_ERR_ARGUMENT_SPLAT_AFTER_SPLAT]         = "unexpected `*` splat argument after a `*` splat argument",
-    [PM_ERR_ARGUMENT_TERM_PAREN]                = "expected a `)` to close the arguments",
-    [PM_ERR_ARGUMENT_UNEXPECTED_BLOCK]          = "unexpected `{` after a method call without parenthesis",
-    [PM_ERR_ARRAY_ELEMENT]                      = "expected an element for the array",
-    [PM_ERR_ARRAY_EXPRESSION]                   = "expected an expression for the array element",
-    [PM_ERR_ARRAY_EXPRESSION_AFTER_STAR]        = "expected an expression after `*` in the array",
-    [PM_ERR_ARRAY_SEPARATOR]                    = "expected a `,` separator for the array elements",
-    [PM_ERR_ARRAY_TERM]                         = "expected a `]` to close the array",
-    [PM_ERR_BEGIN_LONELY_ELSE]                  = "unexpected `else` in `begin` block; a `rescue` clause must precede `else`",
-    [PM_ERR_BEGIN_TERM]                         = "expected an `end` to close the `begin` statement",
-    [PM_ERR_BEGIN_UPCASE_BRACE]                 = "expected a `{` after `BEGIN`",
-    [PM_ERR_BEGIN_UPCASE_TERM]                  = "expected a `}` to close the `BEGIN` statement",
-    [PM_ERR_BEGIN_UPCASE_TOPLEVEL]              = "BEGIN is permitted only at toplevel",
-    [PM_ERR_BLOCK_PARAM_LOCAL_VARIABLE]         = "expected a local variable name in the block parameters",
-    [PM_ERR_BLOCK_PARAM_PIPE_TERM]              = "expected the block parameters to end with `|`",
-    [PM_ERR_BLOCK_TERM_BRACE]                   = "expected a block beginning with `{` to end with `}`",
-    [PM_ERR_BLOCK_TERM_END]                     = "expected a block beginning with `do` to end with `end`",
-    [PM_ERR_CANNOT_PARSE_EXPRESSION]            = "cannot parse the expression",
-    [PM_ERR_CANNOT_PARSE_STRING_PART]           = "cannot parse the string part",
-    [PM_ERR_CASE_EXPRESSION_AFTER_CASE]         = "expected an expression after `case`",
-    [PM_ERR_CASE_EXPRESSION_AFTER_WHEN]         = "expected an expression after `when`",
-    [PM_ERR_CASE_MATCH_MISSING_PREDICATE]       = "expected a predicate for a case matching statement",
-    [PM_ERR_CASE_MISSING_CONDITIONS]            = "expected a `when` or `in` clause after `case`",
-    [PM_ERR_CASE_TERM]                          = "expected an `end` to close the `case` statement",
-    [PM_ERR_CLASS_IN_METHOD]                    = "unexpected class definition in a method definition",
-    [PM_ERR_CLASS_NAME]                         = "expected a constant name after `class`",
-    [PM_ERR_CLASS_SUPERCLASS]                   = "expected a superclass after `<`",
-    [PM_ERR_CLASS_TERM]                         = "expected an `end` to close the `class` statement",
-    [PM_ERR_CLASS_UNEXPECTED_END]               = "unexpected `end`, expecting ';' or '\\n'",
-    [PM_ERR_CONDITIONAL_ELSIF_PREDICATE]        = "expected a predicate expression for the `elsif` statement",
-    [PM_ERR_CONDITIONAL_IF_PREDICATE]           = "expected a predicate expression for the `if` statement",
-    [PM_ERR_CONDITIONAL_PREDICATE_TERM]         = "expected `then` or `;` or '\\n'",
-    [PM_ERR_CONDITIONAL_TERM]                   = "expected an `end` to close the conditional clause",
-    [PM_ERR_CONDITIONAL_TERM_ELSE]              = "expected an `end` to close the `else` clause",
-    [PM_ERR_CONDITIONAL_UNLESS_PREDICATE]       = "expected a predicate expression for the `unless` statement",
-    [PM_ERR_CONDITIONAL_UNTIL_PREDICATE]        = "expected a predicate expression for the `until` statement",
-    [PM_ERR_CONDITIONAL_WHILE_PREDICATE]        = "expected a predicate expression for the `while` statement",
-    [PM_ERR_CONSTANT_PATH_COLON_COLON_CONSTANT] = "expected a constant after the `::` operator",
-    [PM_ERR_DEF_ENDLESS]                        = "could not parse the endless method body",
-    [PM_ERR_DEF_ENDLESS_SETTER]                 = "invalid method name; a setter method cannot be defined in an endless method definition",
-    [PM_ERR_DEF_NAME]                           = "expected a method name",
-    [PM_ERR_DEF_NAME_AFTER_RECEIVER]            = "expected a method name after the receiver",
-    [PM_ERR_DEF_PARAMS_TERM]                    = "expected a delimiter to close the parameters",
-    [PM_ERR_DEF_PARAMS_TERM_PAREN]              = "expected a `)` to close the parameters",
-    [PM_ERR_DEF_RECEIVER]                       = "expected a receiver for the method definition",
-    [PM_ERR_DEF_RECEIVER_TERM]                  = "expected a `.` or `::` after the receiver in a method definition",
-    [PM_ERR_DEF_TERM]                           = "expected an `end` to close the `def` statement",
-    [PM_ERR_DEFINED_EXPRESSION]                 = "expected an expression after `defined?`",
-    [PM_ERR_EMBDOC_TERM]                        = "could not find a terminator for the embedded document",
-    [PM_ERR_EMBEXPR_END]                        = "expected a `}` to close the embedded expression",
-    [PM_ERR_EMBVAR_INVALID]                     = "invalid embedded variable",
-    [PM_ERR_END_UPCASE_BRACE]                   = "expected a `{` after `END`",
-    [PM_ERR_END_UPCASE_TERM]                    = "expected a `}` to close the `END` statement",
-    [PM_ERR_ESCAPE_INVALID_CONTROL]             = "invalid control escape sequence",
-    [PM_ERR_ESCAPE_INVALID_CONTROL_REPEAT]      = "invalid control escape sequence; control cannot be repeated",
-    [PM_ERR_ESCAPE_INVALID_HEXADECIMAL]         = "invalid hexadecimal escape sequence",
-    [PM_ERR_ESCAPE_INVALID_META]                = "invalid meta escape sequence",
-    [PM_ERR_ESCAPE_INVALID_META_REPEAT]         = "invalid meta escape sequence; meta cannot be repeated",
-    [PM_ERR_ESCAPE_INVALID_UNICODE]             = "invalid Unicode escape sequence",
-    [PM_ERR_ESCAPE_INVALID_UNICODE_CM_FLAGS]    = "invalid Unicode escape sequence; Unicode cannot be combined with control or meta flags",
-    [PM_ERR_ESCAPE_INVALID_UNICODE_LITERAL]     = "invalid Unicode escape sequence; multiple codepoints are not allowed in a character literal",
-    [PM_ERR_ESCAPE_INVALID_UNICODE_LONG]        = "invalid Unicode escape sequence; maximum length is 6 digits",
-    [PM_ERR_ESCAPE_INVALID_UNICODE_TERM]        = "invalid Unicode escape sequence; needs closing `}`",
-    [PM_ERR_EXPECT_ARGUMENT]                    = "expected an argument",
-    [PM_ERR_EXPECT_EOL_AFTER_STATEMENT]         = "expected a newline or semicolon after the statement",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_AMPAMPEQ]   = "expected an expression after `&&=`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_PIPEPIPEEQ] = "expected an expression after `||=`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_COMMA]      = "expected an expression after `,`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_EQUAL]      = "expected an expression after `=`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_LESS_LESS]  = "expected an expression after `<<`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_LPAREN]     = "expected an expression after `(`",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_OPERATOR]   = "expected an expression after the operator",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_SPLAT]      = "expected an expression after `*` splat in an argument",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_SPLAT_HASH] = "expected an expression after `**` in a hash",
-    [PM_ERR_EXPECT_EXPRESSION_AFTER_STAR]       = "expected an expression after `*`",
-    [PM_ERR_EXPECT_IDENT_REQ_PARAMETER]         = "expected an identifier for the required parameter",
-    [PM_ERR_EXPECT_LPAREN_REQ_PARAMETER]        = "expected a `(` to start a required parameter",
-    [PM_ERR_EXPECT_RBRACKET]                    = "expected a matching `]`",
-    [PM_ERR_EXPECT_RPAREN]                      = "expected a matching `)`",
-    [PM_ERR_EXPECT_RPAREN_AFTER_MULTI]          = "expected a `)` after multiple assignment",
-    [PM_ERR_EXPECT_RPAREN_REQ_PARAMETER]        = "expected a `)` to end a required parameter",
-    [PM_ERR_EXPECT_STRING_CONTENT]              = "expected string content after opening string delimiter",
-    [PM_ERR_EXPECT_WHEN_DELIMITER]              = "expected a delimiter after the predicates of a `when` clause",
-    [PM_ERR_EXPRESSION_BARE_HASH]               = "unexpected bare hash in expression",
-    [PM_ERR_FOR_COLLECTION]                     = "expected a collection after the `in` in a `for` statement",
-    [PM_ERR_FOR_INDEX]                          = "expected an index after `for`",
-    [PM_ERR_FOR_IN]                             = "expected an `in` after the index in a `for` statement",
-    [PM_ERR_FOR_TERM]                           = "expected an `end` to close the `for` loop",
-    [PM_ERR_HASH_EXPRESSION_AFTER_LABEL]        = "expected an expression after the label in a hash",
-    [PM_ERR_HASH_KEY]                           = "expected a key in the hash literal",
-    [PM_ERR_HASH_ROCKET]                        = "expected a `=>` between the hash key and value",
-    [PM_ERR_HASH_TERM]                          = "expected a `}` to close the hash literal",
-    [PM_ERR_HASH_VALUE]                         = "expected a value in the hash literal",
-    [PM_ERR_HEREDOC_TERM]                       = "could not find a terminator for the heredoc",
-    [PM_ERR_INCOMPLETE_QUESTION_MARK]           = "incomplete expression at `?`",
-    [PM_ERR_INCOMPLETE_VARIABLE_CLASS]          = "incomplete class variable",
-    [PM_ERR_INCOMPLETE_VARIABLE_INSTANCE]       = "incomplete instance variable",
-    [PM_ERR_INVALID_ENCODING_MAGIC_COMMENT]     = "unknown or invalid encoding in the magic comment",
-    [PM_ERR_INVALID_FLOAT_EXPONENT]             = "invalid exponent",
-    [PM_ERR_INVALID_NUMBER_BINARY]              = "invalid binary number",
-    [PM_ERR_INVALID_NUMBER_DECIMAL]             = "invalid decimal number",
-    [PM_ERR_INVALID_NUMBER_HEXADECIMAL]         = "invalid hexadecimal number",
-    [PM_ERR_INVALID_NUMBER_OCTAL]               = "invalid octal number",
-    [PM_ERR_INVALID_NUMBER_UNDERSCORE]          = "invalid underscore placement in number",
-    [PM_ERR_INVALID_PERCENT]                    = "invalid `%` token", // TODO WHAT?
-    [PM_ERR_INVALID_TOKEN]                      = "invalid token", // TODO WHAT?
-    [PM_ERR_INVALID_VARIABLE_GLOBAL]            = "invalid global variable",
-    [PM_ERR_IT_NOT_ALLOWED]                     = "`it` is not allowed when an ordinary parameter is defined",
-    [PM_ERR_LAMBDA_OPEN]                        = "expected a `do` keyword or a `{` to open the lambda block",
-    [PM_ERR_LAMBDA_TERM_BRACE]                  = "expected a lambda block beginning with `{` to end with `}`",
-    [PM_ERR_LAMBDA_TERM_END]                    = "expected a lambda block beginning with `do` to end with `end`",
-    [PM_ERR_LIST_I_LOWER_ELEMENT]               = "expected a symbol in a `%i` list",
-    [PM_ERR_LIST_I_LOWER_TERM]                  = "expected a closing delimiter for the `%i` list",
-    [PM_ERR_LIST_I_UPPER_ELEMENT]               = "expected a symbol in a `%I` list",
-    [PM_ERR_LIST_I_UPPER_TERM]                  = "expected a closing delimiter for the `%I` list",
-    [PM_ERR_LIST_W_LOWER_ELEMENT]               = "expected a string in a `%w` list",
-    [PM_ERR_LIST_W_LOWER_TERM]                  = "expected a closing delimiter for the `%w` list",
-    [PM_ERR_LIST_W_UPPER_ELEMENT]               = "expected a string in a `%W` list",
-    [PM_ERR_LIST_W_UPPER_TERM]                  = "expected a closing delimiter for the `%W` list",
-    [PM_ERR_MALLOC_FAILED]                      = "failed to allocate memory",
-    [PM_ERR_MIXED_ENCODING]                     = "UTF-8 mixed within %s source",
-    [PM_ERR_MODULE_IN_METHOD]                   = "unexpected module definition in a method definition",
-    [PM_ERR_MODULE_NAME]                        = "expected a constant name after `module`",
-    [PM_ERR_MODULE_TERM]                        = "expected an `end` to close the `module` statement",
-    [PM_ERR_MULTI_ASSIGN_MULTI_SPLATS]          = "multiple splats in multiple assignment",
-    [PM_ERR_NOT_EXPRESSION]                     = "expected an expression after `not`",
-    [PM_ERR_NO_LOCAL_VARIABLE]                  = "%.*s: no such local variable",
-    [PM_ERR_NUMBER_LITERAL_UNDERSCORE]          = "number literal ending with a `_`",
-    [PM_ERR_NUMBERED_PARAMETER_NOT_ALLOWED]     = "numbered parameters are not allowed when an ordinary parameter is defined",
-    [PM_ERR_NUMBERED_PARAMETER_OUTER_SCOPE]     = "numbered parameter is already used in outer scope",
-    [PM_ERR_OPERATOR_MULTI_ASSIGN]              = "unexpected operator for a multiple assignment",
-    [PM_ERR_OPERATOR_WRITE_ARGUMENTS]           = "unexpected operator after a call with arguments",
-    [PM_ERR_OPERATOR_WRITE_BLOCK]               = "unexpected operator after a call with a block",
-    [PM_ERR_PARAMETER_ASSOC_SPLAT_MULTI]        = "unexpected multiple `**` splat parameters",
-    [PM_ERR_PARAMETER_BLOCK_MULTI]              = "multiple block parameters; only one block is allowed",
-    [PM_ERR_PARAMETER_CIRCULAR]                 = "parameter default value references itself",
-    [PM_ERR_PARAMETER_METHOD_NAME]              = "unexpected name for a parameter",
-    [PM_ERR_PARAMETER_NAME_REPEAT]              = "repeated parameter name",
-    [PM_ERR_PARAMETER_NO_DEFAULT]               = "expected a default value for the parameter",
-    [PM_ERR_PARAMETER_NO_DEFAULT_KW]            = "expected a default value for the keyword parameter",
-    [PM_ERR_PARAMETER_NUMBERED_RESERVED]        = "%.2s is reserved for numbered parameters",
-    [PM_ERR_PARAMETER_ORDER]                    = "unexpected parameter order",
-    [PM_ERR_PARAMETER_SPLAT_MULTI]              = "unexpected multiple `*` splat parameters",
-    [PM_ERR_PARAMETER_STAR]                     = "unexpected parameter `*`",
-    [PM_ERR_PARAMETER_UNEXPECTED_FWD]           = "unexpected `...` in parameters",
-    [PM_ERR_PARAMETER_WILD_LOOSE_COMMA]         = "unexpected `,` in parameters",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_BRACKET]   = "expected a pattern expression after the `[` operator",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_COMMA]     = "expected a pattern expression after `,`",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_HROCKET]   = "expected a pattern expression after `=>`",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_IN]        = "expected a pattern expression after the `in` keyword",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_KEY]       = "expected a pattern expression after the key",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_PAREN]     = "expected a pattern expression after the `(` operator",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_PIN]       = "expected a pattern expression after the `^` pin operator",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_PIPE]      = "expected a pattern expression after the `|` operator",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_RANGE]     = "expected a pattern expression after the range operator",
-    [PM_ERR_PATTERN_EXPRESSION_AFTER_REST]      = "unexpected pattern expression after the `**` expression",
-    [PM_ERR_PATTERN_HASH_KEY]                   = "expected a key in the hash pattern",
-    [PM_ERR_PATTERN_HASH_KEY_LABEL]             = "expected a label as the key in the hash pattern", // TODO // THIS // AND // ABOVE // IS WEIRD
-    [PM_ERR_PATTERN_IDENT_AFTER_HROCKET]        = "expected an identifier after the `=>` operator",
-    [PM_ERR_PATTERN_LABEL_AFTER_COMMA]          = "expected a label after the `,` in the hash pattern",
-    [PM_ERR_PATTERN_REST]                       = "unexpected rest pattern",
-    [PM_ERR_PATTERN_TERM_BRACE]                 = "expected a `}` to close the pattern expression",
-    [PM_ERR_PATTERN_TERM_BRACKET]               = "expected a `]` to close the pattern expression",
-    [PM_ERR_PATTERN_TERM_PAREN]                 = "expected a `)` to close the pattern expression",
-    [PM_ERR_PIPEPIPEEQ_MULTI_ASSIGN]            = "unexpected `||=` in a multiple assignment",
-    [PM_ERR_REGEXP_TERM]                        = "expected a closing delimiter for the regular expression",
-    [PM_ERR_RESCUE_EXPRESSION]                  = "expected a rescued expression",
-    [PM_ERR_RESCUE_MODIFIER_VALUE]              = "expected a value after the `rescue` modifier",
-    [PM_ERR_RESCUE_TERM]                        = "expected a closing delimiter for the `rescue` clause",
-    [PM_ERR_RESCUE_VARIABLE]                    = "expected an exception variable after `=>` in a rescue statement",
-    [PM_ERR_RETURN_INVALID]                     = "invalid `return` in a class or module body",
-    [PM_ERR_STATEMENT_ALIAS]                    = "unexpected an `alias` at a non-statement position",
-    [PM_ERR_STATEMENT_POSTEXE_END]              = "unexpected an `END` at a non-statement position",
-    [PM_ERR_STATEMENT_PREEXE_BEGIN]             = "unexpected a `BEGIN` at a non-statement position",
-    [PM_ERR_STATEMENT_UNDEF]                    = "unexpected an `undef` at a non-statement position",
-    [PM_ERR_STRING_CONCATENATION]               = "expected a string for concatenation",
-    [PM_ERR_STRING_INTERPOLATED_TERM]           = "expected a closing delimiter for the interpolated string",
-    [PM_ERR_STRING_LITERAL_TERM]                = "expected a closing delimiter for the string literal",
-    [PM_ERR_SYMBOL_INVALID]                     = "invalid symbol", // TODO expected symbol? prism.c ~9719
-    [PM_ERR_SYMBOL_TERM_DYNAMIC]                = "expected a closing delimiter for the dynamic symbol",
-    [PM_ERR_SYMBOL_TERM_INTERPOLATED]           = "expected a closing delimiter for the interpolated symbol",
-    [PM_ERR_TERNARY_COLON]                      = "expected a `:` after the true expression of a ternary operator",
-    [PM_ERR_TERNARY_EXPRESSION_FALSE]           = "expected an expression after `:` in the ternary operator",
-    [PM_ERR_TERNARY_EXPRESSION_TRUE]            = "expected an expression after `?` in the ternary operator",
-    [PM_ERR_UNDEF_ARGUMENT]                     = "invalid argument being passed to `undef`; expected a bare word, constant, or symbol argument",
-    [PM_ERR_UNARY_RECEIVER_BANG]                = "expected a receiver for unary `!`",
-    [PM_ERR_UNARY_RECEIVER_MINUS]               = "expected a receiver for unary `-`",
-    [PM_ERR_UNARY_RECEIVER_PLUS]                = "expected a receiver for unary `+`",
-    [PM_ERR_UNARY_RECEIVER_TILDE]               = "expected a receiver for unary `~`",
-    [PM_ERR_UNTIL_TERM]                         = "expected an `end` to close the `until` statement",
-    [PM_ERR_VOID_EXPRESSION]                    = "unexpected void value expression",
-    [PM_ERR_WHILE_TERM]                         = "expected an `end` to close the `while` statement",
-    [PM_ERR_WRITE_TARGET_IN_METHOD]             = "dynamic constant assignment",
-    [PM_ERR_WRITE_TARGET_READONLY]              = "immutable variable as a write target",
-    [PM_ERR_WRITE_TARGET_UNEXPECTED]            = "unexpected write target",
-    [PM_ERR_XSTRING_TERM]                       = "expected a closing delimiter for the `%x` or backtick string",
-    [PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_MINUS]    = "ambiguous first argument; put parentheses or a space even after `-` operator",
-    [PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_PLUS]     = "ambiguous first argument; put parentheses or a space even after `+` operator",
-    [PM_WARN_AMBIGUOUS_PREFIX_STAR]             = "ambiguous `*` has been interpreted as an argument prefix",
-    [PM_WARN_AMBIGUOUS_SLASH]                   = "ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator",
-    [PM_WARN_END_IN_METHOD]                     = "END in method; use at_exit",
+static struct diagnostic_data const diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
+    // Errors
+    [PM_ERR_ALIAS_ARGUMENT]                     = { "invalid argument being passed to `alias`; expected a bare word, symbol, constant, or global variable", PM_ERROR_DEFAULT },
+    [PM_ERR_AMPAMPEQ_MULTI_ASSIGN]              = { "unexpected `&&=` in a multiple assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_AFTER_BLOCK]               = { "unexpected argument after a block argument", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_AFTER_FORWARDING_ELLIPSES] = { "unexpected argument after `...`", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_BARE_HASH]                 = { "unexpected bare hash argument", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_BLOCK_FORWARDING]          = { "both a block argument and a forwarding argument; only one block is allowed", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_BLOCK_MULTI]               = { "multiple block arguments; only one block is allowed", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_FORMAL_CLASS]              = { "invalid formal argument; formal argument cannot be a class variable", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_FORMAL_CONSTANT]           = { "invalid formal argument; formal argument cannot be a constant", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_FORMAL_GLOBAL]             = { "invalid formal argument; formal argument cannot be a global variable", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_FORMAL_IVAR]               = { "invalid formal argument; formal argument cannot be an instance variable", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_FORWARDING_UNBOUND]        = { "unexpected `...` in an non-parenthesized call", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_IN]                        = { "unexpected `in` keyword in arguments", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_NO_FORWARDING_AMP]         = { "unexpected `&` when the parent method is not forwarding", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_NO_FORWARDING_ELLIPSES]    = { "unexpected `...` when the parent method is not forwarding", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_NO_FORWARDING_STAR]        = { "unexpected `*` when the parent method is not forwarding", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_SPLAT_AFTER_ASSOC_SPLAT]   = { "unexpected `*` splat argument after a `**` keyword splat argument", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_SPLAT_AFTER_SPLAT]         = { "unexpected `*` splat argument after a `*` splat argument", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_TERM_PAREN]                = { "expected a `)` to close the arguments", PM_ERROR_DEFAULT },
+    [PM_ERR_ARGUMENT_UNEXPECTED_BLOCK]          = { "unexpected `{` after a method call without parenthesis", PM_ERROR_DEFAULT },
+    [PM_ERR_ARRAY_ELEMENT]                      = { "expected an element for the array", PM_ERROR_DEFAULT },
+    [PM_ERR_ARRAY_EXPRESSION]                   = { "expected an expression for the array element", PM_ERROR_DEFAULT },
+    [PM_ERR_ARRAY_EXPRESSION_AFTER_STAR]        = { "expected an expression after `*` in the array", PM_ERROR_DEFAULT },
+    [PM_ERR_ARRAY_SEPARATOR]                    = { "expected a `,` separator for the array elements", PM_ERROR_DEFAULT },
+    [PM_ERR_ARRAY_TERM]                         = { "expected a `]` to close the array", PM_ERROR_DEFAULT },
+    [PM_ERR_BEGIN_LONELY_ELSE]                  = { "unexpected `else` in `begin` block; a `rescue` clause must precede `else`", PM_ERROR_DEFAULT },
+    [PM_ERR_BEGIN_TERM]                         = { "expected an `end` to close the `begin` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_BEGIN_UPCASE_BRACE]                 = { "expected a `{` after `BEGIN`", PM_ERROR_DEFAULT },
+    [PM_ERR_BEGIN_UPCASE_TERM]                  = { "expected a `}` to close the `BEGIN` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_BEGIN_UPCASE_TOPLEVEL]              = { "BEGIN is permitted only at toplevel", PM_ERROR_DEFAULT },
+    [PM_ERR_BLOCK_PARAM_LOCAL_VARIABLE]         = { "expected a local variable name in the block parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_BLOCK_PARAM_PIPE_TERM]              = { "expected the block parameters to end with `|`", PM_ERROR_DEFAULT },
+    [PM_ERR_BLOCK_TERM_BRACE]                   = { "expected a block beginning with `{` to end with `}`", PM_ERROR_DEFAULT },
+    [PM_ERR_BLOCK_TERM_END]                     = { "expected a block beginning with `do` to end with `end`", PM_ERROR_DEFAULT },
+    [PM_ERR_CANNOT_PARSE_EXPRESSION]            = { "cannot parse the expression", PM_ERROR_DEFAULT },
+    [PM_ERR_CANNOT_PARSE_STRING_PART]           = { "cannot parse the string part", PM_ERROR_DEFAULT },
+    [PM_ERR_CASE_EXPRESSION_AFTER_CASE]         = { "expected an expression after `case`", PM_ERROR_DEFAULT },
+    [PM_ERR_CASE_EXPRESSION_AFTER_WHEN]         = { "expected an expression after `when`", PM_ERROR_DEFAULT },
+    [PM_ERR_CASE_MATCH_MISSING_PREDICATE]       = { "expected a predicate for a case matching statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CASE_MISSING_CONDITIONS]            = { "expected a `when` or `in` clause after `case`", PM_ERROR_DEFAULT },
+    [PM_ERR_CASE_TERM]                          = { "expected an `end` to close the `case` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CLASS_IN_METHOD]                    = { "unexpected class definition in a method definition", PM_ERROR_DEFAULT },
+    [PM_ERR_CLASS_NAME]                         = { "expected a constant name after `class`", PM_ERROR_DEFAULT },
+    [PM_ERR_CLASS_SUPERCLASS]                   = { "expected a superclass after `<`", PM_ERROR_DEFAULT },
+    [PM_ERR_CLASS_TERM]                         = { "expected an `end` to close the `class` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CLASS_UNEXPECTED_END]               = { "unexpected `end`, expecting ';' or '\\n'", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_ELSIF_PREDICATE]        = { "expected a predicate expression for the `elsif` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_IF_PREDICATE]           = { "expected a predicate expression for the `if` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_PREDICATE_TERM]         = { "expected `then` or `;` or '\\n'", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_TERM]                   = { "expected an `end` to close the conditional clause", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_TERM_ELSE]              = { "expected an `end` to close the `else` clause", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_UNLESS_PREDICATE]       = { "expected a predicate expression for the `unless` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_UNTIL_PREDICATE]        = { "expected a predicate expression for the `until` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CONDITIONAL_WHILE_PREDICATE]        = { "expected a predicate expression for the `while` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_CONSTANT_PATH_COLON_COLON_CONSTANT] = { "expected a constant after the `::` operator", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_ENDLESS]                        = { "could not parse the endless method body", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_ENDLESS_SETTER]                 = { "invalid method name; a setter method cannot be defined in an endless method definition", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_NAME]                           = { "expected a method name", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_NAME_AFTER_RECEIVER]            = { "expected a method name after the receiver", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_PARAMS_TERM]                    = { "expected a delimiter to close the parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_PARAMS_TERM_PAREN]              = { "expected a `)` to close the parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_RECEIVER]                       = { "expected a receiver for the method definition", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_RECEIVER_TERM]                  = { "expected a `.` or `::` after the receiver in a method definition", PM_ERROR_DEFAULT },
+    [PM_ERR_DEF_TERM]                           = { "expected an `end` to close the `def` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_DEFINED_EXPRESSION]                 = { "expected an expression after `defined?`", PM_ERROR_DEFAULT },
+    [PM_ERR_EMBDOC_TERM]                        = { "could not find a terminator for the embedded document", PM_ERROR_DEFAULT },
+    [PM_ERR_EMBEXPR_END]                        = { "expected a `}` to close the embedded expression", PM_ERROR_DEFAULT },
+    [PM_ERR_EMBVAR_INVALID]                     = { "invalid embedded variable", PM_ERROR_DEFAULT },
+    [PM_ERR_END_UPCASE_BRACE]                   = { "expected a `{` after `END`", PM_ERROR_DEFAULT },
+    [PM_ERR_END_UPCASE_TERM]                    = { "expected a `}` to close the `END` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_CONTROL]             = { "invalid control escape sequence", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_CONTROL_REPEAT]      = { "invalid control escape sequence; control cannot be repeated", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_HEXADECIMAL]         = { "invalid hexadecimal escape sequence", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_META]                = { "invalid meta escape sequence", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_META_REPEAT]         = { "invalid meta escape sequence; meta cannot be repeated", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_UNICODE]             = { "invalid Unicode escape sequence", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_UNICODE_CM_FLAGS]    = { "invalid Unicode escape sequence; Unicode cannot be combined with control or meta flags", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_UNICODE_LITERAL]     = { "invalid Unicode escape sequence; multiple codepoints are not allowed in a character literal", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_UNICODE_LONG]        = { "invalid Unicode escape sequence; maximum length is 6 digits", PM_ERROR_DEFAULT },
+    [PM_ERR_ESCAPE_INVALID_UNICODE_TERM]        = { "invalid Unicode escape sequence; needs closing `}`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_ARGUMENT]                    = { "expected an argument", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EOL_AFTER_STATEMENT]         = { "expected a newline or semicolon after the statement", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_AMPAMPEQ]   = { "expected an expression after `&&=`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_PIPEPIPEEQ] = { "expected an expression after `||=`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_COMMA]      = { "expected an expression after `,`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_EQUAL]      = { "expected an expression after `=`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_LESS_LESS]  = { "expected an expression after `<<`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_LPAREN]     = { "expected an expression after `(`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_OPERATOR]   = { "expected an expression after the operator", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_SPLAT]      = { "expected an expression after `*` splat in an argument", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_SPLAT_HASH] = { "expected an expression after `**` in a hash", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_EXPRESSION_AFTER_STAR]       = { "expected an expression after `*`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_IDENT_REQ_PARAMETER]         = { "expected an identifier for the required parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_LPAREN_REQ_PARAMETER]        = { "expected a `(` to start a required parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_RBRACKET]                    = { "expected a matching `]`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_RPAREN]                      = { "expected a matching `)`", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_RPAREN_AFTER_MULTI]          = { "expected a `)` after multiple assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_RPAREN_REQ_PARAMETER]        = { "expected a `)` to end a required parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_STRING_CONTENT]              = { "expected string content after opening string delimiter", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPECT_WHEN_DELIMITER]              = { "expected a delimiter after the predicates of a `when` clause", PM_ERROR_DEFAULT },
+    [PM_ERR_EXPRESSION_BARE_HASH]               = { "unexpected bare hash in expression", PM_ERROR_DEFAULT },
+    [PM_ERR_FOR_COLLECTION]                     = { "expected a collection after the `in` in a `for` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_FOR_INDEX]                          = { "expected an index after `for`", PM_ERROR_DEFAULT },
+    [PM_ERR_FOR_IN]                             = { "expected an `in` after the index in a `for` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_FOR_TERM]                           = { "expected an `end` to close the `for` loop", PM_ERROR_DEFAULT },
+    [PM_ERR_HASH_EXPRESSION_AFTER_LABEL]        = { "expected an expression after the label in a hash", PM_ERROR_DEFAULT },
+    [PM_ERR_HASH_KEY]                           = { "expected a key in the hash literal", PM_ERROR_DEFAULT },
+    [PM_ERR_HASH_ROCKET]                        = { "expected a `=>` between the hash key and value", PM_ERROR_DEFAULT },
+    [PM_ERR_HASH_TERM]                          = { "expected a `}` to close the hash literal", PM_ERROR_DEFAULT },
+    [PM_ERR_HASH_VALUE]                         = { "expected a value in the hash literal", PM_ERROR_DEFAULT },
+    [PM_ERR_HEREDOC_TERM]                       = { "could not find a terminator for the heredoc", PM_ERROR_DEFAULT },
+    [PM_ERR_INCOMPLETE_QUESTION_MARK]           = { "incomplete expression at `?`", PM_ERROR_DEFAULT },
+    [PM_ERR_INCOMPLETE_VARIABLE_CLASS]          = { "incomplete class variable", PM_ERROR_DEFAULT },
+    [PM_ERR_INCOMPLETE_VARIABLE_INSTANCE]       = { "incomplete instance variable", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_ENCODING_MAGIC_COMMENT]     = { "unknown or invalid encoding in the magic comment", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_FLOAT_EXPONENT]             = { "invalid exponent", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_NUMBER_BINARY]              = { "invalid binary number", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_NUMBER_DECIMAL]             = { "invalid decimal number", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_NUMBER_HEXADECIMAL]         = { "invalid hexadecimal number", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_NUMBER_OCTAL]               = { "invalid octal number", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_NUMBER_UNDERSCORE]          = { "invalid underscore placement in number", PM_ERROR_DEFAULT },
+    [PM_ERR_INVALID_PERCENT]                    = { "invalid `%` token", PM_ERROR_DEFAULT }, // TODO WHAT?
+    [PM_ERR_INVALID_TOKEN]                      = { "invalid token", PM_ERROR_DEFAULT }, // TODO WHAT?
+    [PM_ERR_INVALID_VARIABLE_GLOBAL]            = { "invalid global variable", PM_ERROR_DEFAULT },
+    [PM_ERR_IT_NOT_ALLOWED]                     = { "`it` is not allowed when an ordinary parameter is defined", PM_ERROR_DEFAULT },
+    [PM_ERR_LAMBDA_OPEN]                        = { "expected a `do` keyword or a `{` to open the lambda block", PM_ERROR_DEFAULT },
+    [PM_ERR_LAMBDA_TERM_BRACE]                  = { "expected a lambda block beginning with `{` to end with `}`", PM_ERROR_DEFAULT },
+    [PM_ERR_LAMBDA_TERM_END]                    = { "expected a lambda block beginning with `do` to end with `end`", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_I_LOWER_ELEMENT]               = { "expected a symbol in a `%i` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_I_LOWER_TERM]                  = { "expected a closing delimiter for the `%i` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_I_UPPER_ELEMENT]               = { "expected a symbol in a `%I` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_I_UPPER_TERM]                  = { "expected a closing delimiter for the `%I` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_W_LOWER_ELEMENT]               = { "expected a string in a `%w` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_W_LOWER_TERM]                  = { "expected a closing delimiter for the `%w` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_W_UPPER_ELEMENT]               = { "expected a string in a `%W` list", PM_ERROR_DEFAULT },
+    [PM_ERR_LIST_W_UPPER_TERM]                  = { "expected a closing delimiter for the `%W` list", PM_ERROR_DEFAULT },
+    [PM_ERR_MALLOC_FAILED]                      = { "failed to allocate memory", PM_ERROR_DEFAULT },
+    [PM_ERR_MIXED_ENCODING]                     = { "UTF-8 mixed within %s source", PM_ERROR_DEFAULT },
+    [PM_ERR_MODULE_IN_METHOD]                   = { "unexpected module definition in a method definition", PM_ERROR_DEFAULT },
+    [PM_ERR_MODULE_NAME]                        = { "expected a constant name after `module`", PM_ERROR_DEFAULT },
+    [PM_ERR_MODULE_TERM]                        = { "expected an `end` to close the `module` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_MULTI_ASSIGN_MULTI_SPLATS]          = { "multiple splats in multiple assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_NOT_EXPRESSION]                     = { "expected an expression after `not`", PM_ERROR_DEFAULT },
+    [PM_ERR_NO_LOCAL_VARIABLE]                  = { "%.*s: no such local variable", PM_ERROR_DEFAULT },
+    [PM_ERR_NUMBER_LITERAL_UNDERSCORE]          = { "number literal ending with a `_`", PM_ERROR_DEFAULT },
+    [PM_ERR_NUMBERED_PARAMETER_NOT_ALLOWED]     = { "numbered parameters are not allowed when an ordinary parameter is defined", PM_ERROR_DEFAULT },
+    [PM_ERR_NUMBERED_PARAMETER_OUTER_SCOPE]     = { "numbered parameter is already used in outer scope", PM_ERROR_DEFAULT },
+    [PM_ERR_OPERATOR_MULTI_ASSIGN]              = { "unexpected operator for a multiple assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_OPERATOR_WRITE_ARGUMENTS]           = { "unexpected operator after a call with arguments", PM_ERROR_DEFAULT },
+    [PM_ERR_OPERATOR_WRITE_BLOCK]               = { "unexpected operator after a call with a block", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_ASSOC_SPLAT_MULTI]        = { "unexpected multiple `**` splat parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_BLOCK_MULTI]              = { "multiple block parameters; only one block is allowed", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_CIRCULAR]                 = { "parameter default value references itself", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_METHOD_NAME]              = { "unexpected name for a parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_NAME_REPEAT]              = { "repeated parameter name", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_NO_DEFAULT]               = { "expected a default value for the parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_NO_DEFAULT_KW]            = { "expected a default value for the keyword parameter", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_NUMBERED_RESERVED]        = { "%.2s is reserved for numbered parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_ORDER]                    = { "unexpected parameter order", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_SPLAT_MULTI]              = { "unexpected multiple `*` splat parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_STAR]                     = { "unexpected parameter `*`", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_UNEXPECTED_FWD]           = { "unexpected `...` in parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_PARAMETER_WILD_LOOSE_COMMA]         = { "unexpected `,` in parameters", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_BRACKET]   = { "expected a pattern expression after the `[` operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_COMMA]     = { "expected a pattern expression after `,`", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_HROCKET]   = { "expected a pattern expression after `=>`", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_IN]        = { "expected a pattern expression after the `in` keyword", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_KEY]       = { "expected a pattern expression after the key", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_PAREN]     = { "expected a pattern expression after the `(` operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_PIN]       = { "expected a pattern expression after the `^` pin operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_PIPE]      = { "expected a pattern expression after the `|` operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_RANGE]     = { "expected a pattern expression after the range operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_REST]      = { "unexpected pattern expression after the `**` expression", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_HASH_KEY]                   = { "expected a key in the hash pattern", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_HASH_KEY_LABEL]             = { "expected a label as the key in the hash pattern", PM_ERROR_DEFAULT }, // TODO // THIS // AND // ABOVE // IS WEIRD
+    [PM_ERR_PATTERN_IDENT_AFTER_HROCKET]        = { "expected an identifier after the `=>` operator", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_LABEL_AFTER_COMMA]          = { "expected a label after the `,` in the hash pattern", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_REST]                       = { "unexpected rest pattern", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_TERM_BRACE]                 = { "expected a `}` to close the pattern expression", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_TERM_BRACKET]               = { "expected a `]` to close the pattern expression", PM_ERROR_DEFAULT },
+    [PM_ERR_PATTERN_TERM_PAREN]                 = { "expected a `)` to close the pattern expression", PM_ERROR_DEFAULT },
+    [PM_ERR_PIPEPIPEEQ_MULTI_ASSIGN]            = { "unexpected `||=` in a multiple assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_REGEXP_TERM]                        = { "expected a closing delimiter for the regular expression", PM_ERROR_DEFAULT },
+    [PM_ERR_RESCUE_EXPRESSION]                  = { "expected a rescued expression", PM_ERROR_DEFAULT },
+    [PM_ERR_RESCUE_MODIFIER_VALUE]              = { "expected a value after the `rescue` modifier", PM_ERROR_DEFAULT },
+    [PM_ERR_RESCUE_TERM]                        = { "expected a closing delimiter for the `rescue` clause", PM_ERROR_DEFAULT },
+    [PM_ERR_RESCUE_VARIABLE]                    = { "expected an exception variable after `=>` in a rescue statement", PM_ERROR_DEFAULT },
+    [PM_ERR_RETURN_INVALID]                     = { "invalid `return` in a class or module body", PM_ERROR_DEFAULT },
+    [PM_ERR_STATEMENT_ALIAS]                    = { "unexpected an `alias` at a non-statement position", PM_ERROR_DEFAULT },
+    [PM_ERR_STATEMENT_POSTEXE_END]              = { "unexpected an `END` at a non-statement position", PM_ERROR_DEFAULT },
+    [PM_ERR_STATEMENT_PREEXE_BEGIN]             = { "unexpected a `BEGIN` at a non-statement position", PM_ERROR_DEFAULT },
+    [PM_ERR_STATEMENT_UNDEF]                    = { "unexpected an `undef` at a non-statement position", PM_ERROR_DEFAULT },
+    [PM_ERR_STRING_CONCATENATION]               = { "expected a string for concatenation", PM_ERROR_DEFAULT },
+    [PM_ERR_STRING_INTERPOLATED_TERM]           = { "expected a closing delimiter for the interpolated string", PM_ERROR_DEFAULT },
+    [PM_ERR_STRING_LITERAL_TERM]                = { "expected a closing delimiter for the string literal", PM_ERROR_DEFAULT },
+    [PM_ERR_SYMBOL_INVALID]                     = { "invalid symbol", PM_ERROR_DEFAULT }, // TODO expected symbol? prism.c ~9719
+    [PM_ERR_SYMBOL_TERM_DYNAMIC]                = { "expected a closing delimiter for the dynamic symbol", PM_ERROR_DEFAULT },
+    [PM_ERR_SYMBOL_TERM_INTERPOLATED]           = { "expected a closing delimiter for the interpolated symbol", PM_ERROR_DEFAULT },
+    [PM_ERR_TERNARY_COLON]                      = { "expected a `:` after the true expression of a ternary operator", PM_ERROR_DEFAULT },
+    [PM_ERR_TERNARY_EXPRESSION_FALSE]           = { "expected an expression after `:` in the ternary operator", PM_ERROR_DEFAULT },
+    [PM_ERR_TERNARY_EXPRESSION_TRUE]            = { "expected an expression after `?` in the ternary operator", PM_ERROR_DEFAULT },
+    [PM_ERR_UNDEF_ARGUMENT]                     = { "invalid argument being passed to `undef`; expected a bare word, constant, or symbol argument", PM_ERROR_DEFAULT },
+    [PM_ERR_UNARY_RECEIVER_BANG]                = { "expected a receiver for unary `!`", PM_ERROR_DEFAULT },
+    [PM_ERR_UNARY_RECEIVER_MINUS]               = { "expected a receiver for unary `-`", PM_ERROR_DEFAULT },
+    [PM_ERR_UNARY_RECEIVER_PLUS]                = { "expected a receiver for unary `+`", PM_ERROR_DEFAULT },
+    [PM_ERR_UNARY_RECEIVER_TILDE]               = { "expected a receiver for unary `~`", PM_ERROR_DEFAULT },
+    [PM_ERR_UNTIL_TERM]                         = { "expected an `end` to close the `until` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_VOID_EXPRESSION]                    = { "unexpected void value expression", PM_ERROR_DEFAULT },
+    [PM_ERR_WHILE_TERM]                         = { "expected an `end` to close the `while` statement", PM_ERROR_DEFAULT },
+    [PM_ERR_WRITE_TARGET_IN_METHOD]             = { "dynamic constant assignment", PM_ERROR_DEFAULT },
+    [PM_ERR_WRITE_TARGET_READONLY]              = { "immutable variable as a write target", PM_ERROR_DEFAULT },
+    [PM_ERR_WRITE_TARGET_UNEXPECTED]            = { "unexpected write target", PM_ERROR_DEFAULT },
+    [PM_ERR_XSTRING_TERM]                       = { "expected a closing delimiter for the `%x` or backtick string", PM_ERROR_DEFAULT },
+    // Warnings
+    [PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_MINUS]    = { "ambiguous first argument; put parentheses or a space even after `-` operator", PM_WARNING_VERBOSE_TRUE },
+    [PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_PLUS]     = { "ambiguous first argument; put parentheses or a space even after `+` operator", PM_WARNING_VERBOSE_TRUE },
+    [PM_WARN_AMBIGUOUS_PREFIX_STAR]             = { "ambiguous `*` has been interpreted as an argument prefix", PM_WARNING_VERBOSE_TRUE },
+    [PM_WARN_AMBIGUOUS_SLASH]                   = { "ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator", PM_WARNING_VERBOSE_TRUE },
+    [PM_WARN_END_IN_METHOD]                     = { "END in method; use at_exit", PM_WARNING_VERBOSE_NOT_NIL },
 };
 
 static const char*
 pm_diagnostic_message(pm_diagnostic_id_t diag_id) {
     assert(diag_id < PM_DIAGNOSTIC_ID_LEN);
 
-    const char *message = diagnostic_messages[diag_id];
+    const char *message = diagnostic_messages[diag_id].message;
     assert(message);
 
     return message;
 }
 
+static uint8_t
+pm_diagnostic_level(pm_diagnostic_id_t diag_id) {
+    assert(diag_id < PM_DIAGNOSTIC_ID_LEN);
+
+    return (uint8_t) diagnostic_messages[diag_id].level;
+}
+
 /**
  * Append an error to the given list of diagnostic.
  */
@@ -292,7 +317,8 @@ pm_diagnostic_list_append(pm_list_t *list, const uint8_t *start, const uint8_t *
     *diagnostic = (pm_diagnostic_t) {
         .location = { start, end },
         .message = pm_diagnostic_message(diag_id),
-        .owned = false
+        .owned = false,
+        .level = pm_diagnostic_level(diag_id)
     };
 
     pm_list_append(list, (pm_list_node_t *) diagnostic);
@@ -335,7 +361,8 @@ pm_diagnostic_list_append_format(pm_list_t *list, const uint8_t *start, const ui
     *diagnostic = (pm_diagnostic_t) {
         .location = { start, end },
         .message = message,
-        .owned = true
+        .owned = true,
+        .level = pm_diagnostic_level(diag_id)
     };
 
     pm_list_append(list, (pm_list_node_t *) diagnostic);
diff --git a/prism/diagnostic.h b/prism/diagnostic.h
index fb41102361..19395176ac 100644
--- a/prism/diagnostic.h
+++ b/prism/diagnostic.h
@@ -15,6 +15,18 @@
 #include <assert.h>
 
 /**
+ * This enum represents the level of diagnostics generated during parsing.
+ */
+typedef enum {
+    /** The default level for errors. */
+    PM_ERROR_DEFAULT = 0,
+    /** For warnings which should be emitted if $VERBOSE != nil. */
+    PM_WARNING_VERBOSE_NOT_NIL = 1,
+    /** For warnings which should be emitted if $VERBOSE == true. */
+    PM_WARNING_VERBOSE_TRUE = 2
+} pm_diagnostic_level_t;
+
+/**
  * This struct represents a diagnostic generated during parsing.
  *
  * @extends pm_list_node_t
@@ -35,6 +47,9 @@ typedef struct {
      * diagnostic is freed.
      */
     bool owned;
+
+    /** The level of the diagnostic, see pm_diagnostic_level_t for possible values. */
+    uint8_t level;
 } pm_diagnostic_t;
 
 /**
diff --git a/prism/extension.c b/prism/extension.c
index 416e682f76..72be59bc6d 100644
--- a/prism/extension.c
+++ b/prism/extension.c
@@ -368,6 +368,19 @@ parser_magic_comments(pm_parser_t *parser, VALUE source) {
     return magic_comments;
 }
 
+static VALUE get_diagnostic_level_symbol(uint8_t level) {
+    switch (level) {
+        case 0:
+            return ID2SYM(rb_intern("error_default"));
+        case 1:
+            return ID2SYM(rb_intern("warning_verbose_not_nil"));
+        case 2:
+            return ID2SYM(rb_intern("warning_verbose_true"));
+        default:
+            rb_raise(rb_eRuntimeError, "Unknown level: %" PRIu8, level);
+    }
+}
+
 /**
  * Extract out the data location from the parser into a Location instance if one
  * exists.
@@ -404,10 +417,11 @@ parser_errors(pm_parser_t *parser, rb_encoding *encoding, VALUE source) {
 
         VALUE error_argv[] = {
             rb_enc_str_new_cstr(error->message, encoding),
-            rb_class_new_instance(3, location_argv, rb_cPrismLocation)
+            rb_class_new_instance(3, location_argv, rb_cPrismLocation),
+            get_diagnostic_level_symbol(error->level)
         };
 
-        rb_ary_push(errors, rb_class_new_instance(2, error_argv, rb_cPrismParseError));
+        rb_ary_push(errors, rb_class_new_instance(3, error_argv, rb_cPrismParseError));
     }
 
     return errors;
@@ -430,10 +444,11 @@ parser_warnings(pm_parser_t *parser, rb_encoding *encoding, VALUE source) {
 
         VALUE warning_argv[] = {
             rb_enc_str_new_cstr(warning->message, encoding),
-            rb_class_new_instance(3, location_argv, rb_cPrismLocation)
+            rb_class_new_instance(3, location_argv, rb_cPrismLocation),
+            get_diagnostic_level_symbol(warning->level)
         };
 
-        rb_ary_push(warnings, rb_class_new_instance(2, warning_argv, rb_cPrismParseWarning));
+        rb_ary_push(warnings, rb_class_new_instance(3, warning_argv, rb_cPrismParseWarning));
     }
 
     return warnings;
diff --git a/prism/templates/lib/prism/serialize.rb.erb b/prism/templates/lib/prism/serialize.rb.erb
index 0b5300c4c5..35b5b4ddb0 100644
--- a/prism/templates/lib/prism/serialize.rb.erb
+++ b/prism/templates/lib/prism/serialize.rb.erb
@@ -96,8 +96,8 @@ module Prism
         comments = load_comments
         magic_comments = load_varuint.times.map { MagicComment.new(load_location, load_location) }
         data_loc = load_optional_location
-        errors = load_varuint.times.map { ParseError.new(load_embedded_string, load_location) }
-        warnings = load_varuint.times.map { ParseWarning.new(load_embedded_string, load_location) }
+        errors = load_varuint.times.map { ParseError.new(load_embedded_string, load_location, load_diagnostic_level) }
+        warnings = load_varuint.times.map { ParseWarning.new(load_embedded_string, load_location, load_diagnostic_level) }
         [comments, magic_comments, data_loc, errors, warnings]
       end
 
@@ -231,6 +231,20 @@ module Prism
         load_constant(index - 1) if index != 0
       end
 
+      def load_diagnostic_level
+        level = io.getbyte
+        case level
+        when 0
+          :error_default
+        when 1
+          :warning_verbose_not_nil
+        when 2
+          :warning_verbose_true
+        else
+          raise "Unknown level: #{level}"
+        end
+      end
+
       if RUBY_ENGINE == 'ruby'
         def load_node
           type = io.getbyte
diff --git a/prism/templates/src/serialize.c.erb b/prism/templates/src/serialize.c.erb
index e9cdd1e82c..deda01f29c 100644
--- a/prism/templates/src/serialize.c.erb
+++ b/prism/templates/src/serialize.c.erb
@@ -190,6 +190,8 @@ pm_serialize_diagnostic(pm_parser_t *parser, pm_diagnostic_t *diagnostic, pm_buf
 
     // serialize location
     pm_serialize_location(parser, &diagnostic->location, buffer);
+
+    pm_buffer_append_byte(buffer, diagnostic->level);
 }
 
 static void
diff --git a/test/prism/errors_test.rb b/test/prism/errors_test.rb
index 304d55274e..b7215c755d 100644
--- a/test/prism/errors_test.rb
+++ b/test/prism/errors_test.rb
@@ -1871,6 +1871,16 @@ module Prism
       ]
     end
 
+    def test_warnings_verbosity
+      warning = Prism.parse("def foo; END { }; end").warnings[0]
+      assert_equal "END in method; use at_exit", warning.message
+      assert_equal :warning_verbose_not_nil, warning.level
+
+      warning = Prism.parse("foo /regexp/").warnings[0]
+      assert_equal "ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator", warning.message
+      assert_equal :warning_verbose_true, warning.level
+    end
+
     def test_statement_operators
       source = <<~RUBY
         alias x y + 1