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Parsing support for if expressions. (#2883)

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We model `if a then b else` as a prefix operator for parsing precedence purposes. The rule that a statement starting with `if` is never an `if` expression is handled implicitly because the statement parser never invokes the expression parser for a statement starting with `if`.

This exposed a bug in our diagnosis of the whitespace rule for prefix operators, which was incorrectly being applied to non-symbolic operators in some cases, and was producing a bogus second diagnostic in some cases, which is also fixed here.
This commit is contained in:
Richard Smith
2023-06-09 16:41:10 -07:00
committed by GitHub
parent 4e1adcf4c7
commit 2c45cb3be8
18 changed files with 400 additions and 22 deletions
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toolchain/parser/testdata/operators/missing_precedence_not.carbon → toolchain/parser/testdata/operators/precedence_not.carbon
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-3
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@@ -23,8 +23,5 @@
// CHECK:STDOUT: ]
fn F() {
// CHECK:STDERR: missing_precedence_not.carbon:[[@LINE+3]]:3: Whitespace is required before this unary operator.
// CHECK:STDERR: missing_precedence_not.carbon:[[@LINE+2]]:13: Whitespace is required before this unary operator.
// CHECK:STDERR: missing_precedence_not.carbon:[[@LINE+1]]:23: Whitespace is required before this unary operator.
not a and not b and not c;
}
toolchain/parser/testdata/operators/recover_postfix_space_surrounding.carbon
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+1 -2
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@@ -15,6 +15,5 @@
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDERR: recover_postfix_space_surrounding.carbon:[[@LINE+2]]:18: Whitespace is not allowed before this unary operator.
// CHECK:STDERR: recover_postfix_space_surrounding.carbon:[[@LINE+1]]:18: Whitespace is required after this unary operator.
// CHECK:STDERR: recover_postfix_space_surrounding.carbon:[[@LINE+1]]:18: Whitespace is not allowed before this unary operator.
var v: type = i8 * ;
toolchain/parser/testdata/operators/recover_prefix_space.carbon
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+1 -2
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@@ -15,6 +15,5 @@
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDERR: recover_prefix_space.carbon:[[@LINE+2]]:13: Whitespace is not allowed after this unary operator.
// CHECK:STDERR: recover_prefix_space.carbon:[[@LINE+1]]:13: Whitespace is required before this unary operator.
// CHECK:STDERR: recover_prefix_space.carbon:[[@LINE+1]]:13: Whitespace is not allowed after this unary operator.
var n: i8 = - n;