Reject import assert in parser and remove checker assert-specific logic

Error at parse time when 'assert' keyword is used for import attributes
(in all 3 parse locations: tryParseImportAttributes, parseExportDeclaration,
parseImportType). Remove checker logic that distinguished between 'assert'
and 'with' tokens, always using 'import attributes' messages.

Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>

Author: Copilot

internal/checker/checker.go

@@ -3231,9 +3231,7 @@ func (c *Checker) checkImportType(node *ast.Node) {
 func (c *Checker) getResolutionModeOverride(node *ast.ImportAttributes, reportErrors bool) core.ResolutionMode {
 	if len(node.Attributes.Nodes) != 1 {
 		if reportErrors {
-			c.grammarErrorOnNode(node.AsNode(), core.IfElse(node.Token == ast.KindWithKeyword,
-				diagnostics.Type_import_attributes_should_have_exactly_one_key_resolution_mode_with_value_import_or_require,
-				diagnostics.Type_import_assertions_should_have_exactly_one_key_resolution_mode_with_value_import_or_require))
+			c.grammarErrorOnNode(node.AsNode(), diagnostics.Type_import_attributes_should_have_exactly_one_key_resolution_mode_with_value_import_or_require)
 		}
 		return core.ResolutionModeNone
 	}
@@ -3243,9 +3241,7 @@ func (c *Checker) getResolutionModeOverride(node *ast.ImportAttributes, reportEr
 	}
 	if elem.Name().Text() != "resolution-mode" {
 		if reportErrors {
-			c.grammarErrorOnNode(elem.Name(), core.IfElse(node.Token == ast.KindWithKeyword,
-				diagnostics.X_resolution_mode_is_the_only_valid_key_for_type_import_attributes,
-				diagnostics.X_resolution_mode_is_the_only_valid_key_for_type_import_assertions))
+			c.grammarErrorOnNode(elem.Name(), diagnostics.X_resolution_mode_is_the_only_valid_key_for_type_import_attributes)
 		}
 		return core.ResolutionModeNone
 	}
@@ -5207,14 +5203,11 @@ func (c *Checker) checkExternalImportOrExportDeclaration(node *ast.Node) bool {
 	if !ast.IsImportEqualsDeclaration(node) {
 		attributes := ast.GetImportAttributes(node)
 		if attributes != nil {
-			diagnostic := core.IfElse(attributes.AsImportAttributes().Token == ast.KindWithKeyword,
-				diagnostics.Import_attribute_values_must_be_string_literal_expressions,
-				diagnostics.Import_assertion_values_must_be_string_literal_expressions)
 			hasError := false
 			for _, attr := range attributes.AsImportAttributes().Attributes.Nodes {
 				if !ast.IsStringLiteral(attr.AsImportAttribute().Value) {
 					hasError = true
-					c.error(attr.AsImportAttribute().Value, diagnostic)
+					c.error(attr.AsImportAttribute().Value, diagnostics.Import_attribute_values_must_be_string_literal_expressions)
 				}
 			}
 			return !hasError
@@ -5260,40 +5253,24 @@ func (c *Checker) checkImportAttributes(declaration *ast.Node) {
 	}
 	isTypeOnly := ast.IsExclusivelyTypeOnlyImportOrExport(declaration)
 	override := c.getResolutionModeOverride(node.AsImportAttributes(), isTypeOnly)
-	isImportAttributes := node.AsImportAttributes().Token == ast.KindWithKeyword
 	if isTypeOnly && override != core.ResolutionModeNone {
 		return // Other grammar checks do not apply to type-only imports with resolution mode assertions
 	}
 
 	if !c.moduleKind.SupportsImportAttributes() {
-		if isImportAttributes {
-			c.grammarErrorOnNode(node, diagnostics.Import_attributes_are_only_supported_when_the_module_option_is_set_to_esnext_node18_node20_nodenext_or_preserve)
-		} else {
-			c.grammarErrorOnNode(node, diagnostics.Import_assertions_are_only_supported_when_the_module_option_is_set_to_esnext_node18_node20_nodenext_or_preserve)
-		}
-		return
-	}
-
-	if core.ModuleKindNode20 <= c.moduleKind && c.moduleKind <= core.ModuleKindNodeNext && !isImportAttributes {
-		c.grammarErrorOnNode(node, diagnostics.Import_assertions_have_been_replaced_by_import_attributes_Use_with_instead_of_assert)
+		c.grammarErrorOnNode(node, diagnostics.Import_attributes_are_only_supported_when_the_module_option_is_set_to_esnext_node18_node20_nodenext_or_preserve)
 		return
 	}
 
 	if moduleSpecifier := getModuleSpecifierFromNode(declaration); moduleSpecifier != nil {
 		if c.getEmitSyntaxForModuleSpecifierExpression(moduleSpecifier) == core.ModuleKindCommonJS {
-			if isImportAttributes {
-				c.grammarErrorOnNode(node, diagnostics.Import_attributes_are_not_allowed_on_statements_that_compile_to_CommonJS_require_calls)
-			} else {
-				c.grammarErrorOnNode(node, diagnostics.Import_assertions_are_not_allowed_on_statements_that_compile_to_CommonJS_require_calls)
-			}
+			c.grammarErrorOnNode(node, diagnostics.Import_attributes_are_not_allowed_on_statements_that_compile_to_CommonJS_require_calls)
 			return
 		}
 	}
 
 	if isTypeOnly {
-		c.grammarErrorOnNode(node, core.IfElse(isImportAttributes,
-			diagnostics.Import_attributes_cannot_be_used_with_type_only_imports_or_exports,
-			diagnostics.Import_assertions_cannot_be_used_with_type_only_imports_or_exports))
+		c.grammarErrorOnNode(node, diagnostics.Import_attributes_cannot_be_used_with_type_only_imports_or_exports)
 		return
 	}
 	if override != core.ResolutionModeNone {

internal/parser/parser.go

@@ -2379,6 +2379,9 @@ func (p *Parser) parseModuleExportName(disallowKeywords bool) (node *ast.Node, n
 
 func (p *Parser) tryParseImportAttributes() *ast.Node {
 	if p.token == ast.KindWithKeyword || (p.token == ast.KindAssertKeyword && !p.hasPrecedingLineBreak()) {
+		if p.token == ast.KindAssertKeyword {
+			p.parseErrorAtCurrentToken(diagnostics.Import_assertions_have_been_replaced_by_import_attributes_Use_with_instead_of_assert)
+		}
 		return p.parseImportAttributes(p.token, false /*skipKeyword*/)
 	}
 	return nil
@@ -2443,6 +2446,9 @@ func (p *Parser) parseExportDeclaration(pos int, hasJSDoc bool, modifiers *ast.M
 		}
 	}
 	if moduleSpecifier != nil && (p.token == ast.KindWithKeyword || p.token == ast.KindAssertKeyword) && !p.hasPrecedingLineBreak() {
+		if p.token == ast.KindAssertKeyword {
+			p.parseErrorAtCurrentToken(diagnostics.Import_assertions_have_been_replaced_by_import_attributes_Use_with_instead_of_assert)
+		}
 		attributes = p.parseImportAttributes(p.token, false /*skipKeyword*/)
 	}
 	p.parseSemicolon()
@@ -2914,6 +2920,9 @@ func (p *Parser) parseImportType() *ast.Node {
 		p.parseExpected(ast.KindOpenBraceToken)
 		currentToken := p.token
 		if currentToken == ast.KindWithKeyword || currentToken == ast.KindAssertKeyword {
+			if currentToken == ast.KindAssertKeyword {
+				p.parseErrorAtCurrentToken(diagnostics.Import_assertions_have_been_replaced_by_import_attributes_Use_with_instead_of_assert)
+			}
 			p.nextToken()
 		} else {
 			p.parseErrorAtCurrentToken(diagnostics.X_0_expected, scanner.TokenToString(ast.KindWithKeyword))

testdata/baselines/reference/submodule/compiler/importAssertionsDeprecated.errors.txt

@@ -0,0 +1,29 @@
+/a.ts(1,35): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+/b.ts(1,37): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+/c.ts(1,51): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+
+
+==== /a.ts (1 errors) ====
+    import json from "./package.json" assert { type: "json" };
+                                      ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /b.ts (1 errors) ====
+    import * as data from "./data.json" assert { type: "json" };
+                                        ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /c.ts (1 errors) ====
+    export { default as config } from "./config.json" assert { type: "json" };
+                                                      ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /package.json (0 errors) ====
+    {}
+    
+==== /data.json (0 errors) ====
+    {}
+    
+==== /config.json (0 errors) ====
+    {}
+    

testdata/baselines/reference/submodule/compiler/importAssertionsDeprecated.errors.txt.diff

@@ -0,0 +1,30 @@
+/a.ts(2,35): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+/b.ts(1,37): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+/c.ts(1,51): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+
+
+==== /a.ts (1 errors) ====
+    // With ignoreDeprecations: "6.0", import assertions should not produce a deprecation error.
+    import json from "./package.json" assert { type: "json" };
+                                      ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /b.ts (1 errors) ====
+    import * as data from "./data.json" assert { type: "json" };
+                                        ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /c.ts (1 errors) ====
+    export { default as config } from "./config.json" assert { type: "json" };
+                                                      ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+    
+==== /package.json (0 errors) ====
+    {}
+    
+==== /data.json (0 errors) ====
+    {}
+    
+==== /config.json (0 errors) ====
+    {}
+    

testdata/baselines/reference/submodule/compiler/importAssertionsDeprecatedIgnored.errors.txt

@@ -0,0 +1,34 @@
+--- old.importAssertionsDeprecatedIgnored.errors.txt
++++ new.importAssertionsDeprecatedIgnored.errors.txt
+@@= skipped -0, +0 lines =@@
+-<no content>
++/a.ts(2,35): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++/b.ts(1,37): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++/c.ts(1,51): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++
++
++==== /a.ts (1 errors) ====
++    // With ignoreDeprecations: "6.0", import assertions should not produce a deprecation error.
++    import json from "./package.json" assert { type: "json" };
++                                      ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++    
++==== /b.ts (1 errors) ====
++    import * as data from "./data.json" assert { type: "json" };
++                                        ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++    
++==== /c.ts (1 errors) ====
++    export { default as config } from "./config.json" assert { type: "json" };
++                                                      ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
++    
++==== /package.json (0 errors) ====
++    {}
++    
++==== /data.json (0 errors) ====
++    {}
++    
++==== /config.json (0 errors) ====
++    {}
++    

testdata/baselines/reference/submodule/compiler/importAssertionsDeprecatedIgnored.errors.txt.diff

@@ -1,4 +1,5 @@
 /index.ts(2,7): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+/index.ts(2,23): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
 /index.ts(2,32): error TS1478: Identifier or string literal expected.
 /index.ts(2,32): error TS2695: Left side of comma operator is unused and has no side effects.
 /index.ts(2,55): error TS1005: ';' expected.
@@ -10,6 +11,7 @@
 /index.ts(3,36): error TS1005: ':' expected.
 /index.ts(3,70): error TS2339: Property 'ImportInterface' does not exist on type 'Promise<{ default: typeof import("/node_modules/pkg/import"); }>'.
 /index.ts(5,34): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+/index.ts(5,50): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
 /index.ts(5,59): error TS1478: Identifier or string literal expected.
 /index.ts(5,59): error TS2695: Left side of comma operator is unused and has no side effects.
 /index.ts(5,82): error TS1005: ';' expected.
@@ -21,6 +23,7 @@
 /index.ts(5,98): error TS2304: Cannot find name 'RequireInterface'.
 /index.ts(5,114): error TS1128: Declaration or statement expected.
 /index.ts(6,34): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+/index.ts(6,50): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
 /index.ts(6,59): error TS1478: Identifier or string literal expected.
 /index.ts(6,59): error TS2695: Left side of comma operator is unused and has no side effects.
 /index.ts(6,82): error TS1005: ';' expected.
@@ -33,11 +36,13 @@
 /index.ts(6,112): error TS1128: Declaration or statement expected.
 
 
-==== /index.ts (33 errors) ====
+==== /index.ts (36 errors) ====
     export type LocalInterface =
         & import("pkg", { assert: {1234, "resolution-mode": "require"} }).RequireInterface
           ~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+                          ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
                                    ~~~~
 !!! error TS1478: Identifier or string literal expected.
                                    ~~~~
@@ -63,6 +68,8 @@
     export const a = (null as any as import("pkg", { assert: {1234, "resolution-mode": "require"} }).RequireInterface);
                                      ~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+                                                     ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
                                                               ~~~~
 !!! error TS1478: Identifier or string literal expected.
                                                               ~~~~
@@ -86,6 +93,8 @@
     export const b = (null as any as import("pkg", { assert: {1234, "resolution-mode": "import"} }).ImportInterface);
                                      ~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
+                                                     ~~~~~~
+!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
                                                               ~~~~
 !!! error TS1478: Identifier or string literal expected.
                                                               ~~~~

testdata/baselines/reference/submodule/compiler/parseAssertEntriesError.errors.txt

@@ -0,0 +1,57 @@
+--- old.parseAssertEntriesError.errors.txt
++++ new.parseAssertEntriesError.errors.txt
+@@= skipped -0, +0 lines =@@
+ /index.ts(2,7): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++/index.ts(2,23): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+ /index.ts(2,32): error TS1478: Identifier or string literal expected.
+ /index.ts(2,32): error TS2695: Left side of comma operator is unused and has no side effects.
+ /index.ts(2,55): error TS1005: ';' expected.
+@@= skipped -9, +10 lines =@@
+ /index.ts(3,36): error TS1005: ':' expected.
+ /index.ts(3,70): error TS2339: Property 'ImportInterface' does not exist on type 'Promise<{ default: typeof import("/node_modules/pkg/import"); }>'.
+ /index.ts(5,34): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++/index.ts(5,50): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+ /index.ts(5,59): error TS1478: Identifier or string literal expected.
+ /index.ts(5,59): error TS2695: Left side of comma operator is unused and has no side effects.
+ /index.ts(5,82): error TS1005: ';' expected.
+@@= skipped -11, +12 lines =@@
+ /index.ts(5,98): error TS2304: Cannot find name 'RequireInterface'.
+ /index.ts(5,114): error TS1128: Declaration or statement expected.
+ /index.ts(6,34): error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++/index.ts(6,50): error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+ /index.ts(6,59): error TS1478: Identifier or string literal expected.
+ /index.ts(6,59): error TS2695: Left side of comma operator is unused and has no side effects.
+ /index.ts(6,82): error TS1005: ';' expected.
+@@= skipped -12, +13 lines =@@
+ /index.ts(6,112): error TS1128: Declaration or statement expected.
+
+
+-==== /index.ts (33 errors) ====
++==== /index.ts (36 errors) ====
+     export type LocalInterface =
+         & import("pkg", { assert: {1234, "resolution-mode": "require"} }).RequireInterface
+           ~~~~~~~~~~~~~~~~~~~~~~~~~
+ !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++                          ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+                                    ~~~~
+ !!! error TS1478: Identifier or string literal expected.
+                                    ~~~~
+@@= skipped -30, +32 lines =@@
+     export const a = (null as any as import("pkg", { assert: {1234, "resolution-mode": "require"} }).RequireInterface);
+                                      ~~~~~~~~~~~~~~~~~~~~~~~~~
+ !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++                                                     ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+                                                               ~~~~
+ !!! error TS1478: Identifier or string literal expected.
+                                                               ~~~~
+@@= skipped -23, +25 lines =@@
+     export const b = (null as any as import("pkg", { assert: {1234, "resolution-mode": "import"} }).ImportInterface);
+                                      ~~~~~~~~~~~~~~~~~~~~~~~~~
+ !!! error TS1340: Module 'pkg' does not refer to a type, but is used as a type here. Did you mean 'typeof import('pkg')'?
++                                                     ~~~~~~
++!!! error TS2880: Import assertions have been replaced by import attributes. Use 'with' instead of 'assert'.
+                                                               ~~~~
+ !!! error TS1478: Identifier or string literal expected.
+                                                               ~~~~